In order to estimate the average time high school students are currently spending on social media, data were collected from a sample of 81 students over a one-week period. Based on prior studies, the population standard deviation can be assumed to be 1.2 hours.
If the sample mean is 9 hours, then the 95% confidence interval is approximately _____.
Select one:
a. 8.74 to 9.26 hours
b. 7.04 to 110.96 hours
c. 7.36 to 10.64 hours
d. 7.80 to 10.20 hours
Solution :
Given that,
Sample size = n = 81
Z/2 = 1.96
Margin of error = E = Z/2* ( /n)
= 1.96 * (1.2 / 81)
Margin of error = E = 0.26
At 95% confidence interval estimate of the population mean is,
- E < < + E
9 - 0.26 < < 9 + 0.26
8.74 < < 9.26
8.74 to 9.26 hours
option a. is correct
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